EFFECT OF SOLVENT SYSTEM ON MICROFLUIDIZATION-INDUCED MECHANICAL DEGRADATION

The microfluidization-induced mechanical degradation of tragacanth was studied under constant processing conditions and in a variety of solvent media. Tragacanth solutions (200 mg%) in water-alcohol cosolvent systems including (in mole fraction alcohol) 0-0.1 methanol, 0-0.072 ethanol, 0-0.015 1-butanol, 0-0.026 isopropanol and 0-0.012 isobutanol were exposed to four cycles of microfluidization (M110T Microfluidizer, high pressure pump, 12 500 lb inch-2 interaction chamber, 23-degrees-C). Samples were removed after each pass and average molecular weight was estimated using photon correlation spectroscopy. The incorporation of alcohol into the bulk media increased both the bulk cosolvent viscosity and the excluded volume of the solvent system. In all cases within, at low alcohol concentrations increased bulk viscosity appears related to increases in the apparent mechanical degradation rate constants. At higher alcohol concentrations the increased excluded volume appears to decrease the apparent mechanical degradation rate constants. These effects appear to be dependent on alcohol size and/or hydrophobicity.